You would have to spend for shipping, but I had a very good experience with Pelham Saddlery.
I did tracings and took pictures of my horse’s back. The knowledgeable staff there immediately knew that some of the saddles I had looked at online wouldn’t work for the shape of his back. Even when I decided that I liked a saddle, they looked at pictures of it on him, extended the trial, and consulted with the fitter to make sure it was workable before we finalized the deal. They could have easily just taken the money for the saddle, but they wanted to make sure that it was right.
I was close enough to make the trip to the store, but they do a lot of remote work too. I know they have several Black Country dressage saddles on consignment, so you might find your saddle from there.